The present invention relates to a developing apparatus for a copier, a printer, etc. based on an electrophotographic process.
Conventionally, U.S. Pat. No. 4,864,349 has proposed a developing apparatus in which first, second and third transport passages are sequentially arranged in parallel and rearwards of a developing section provided with a developing sleeve such that developer is transported through its circulation by the first to third transport passages.
However, in this known developing apparatus, such a phenomenon may take place in which toner transported in each transport passage is used for development in a state where the toner is neither fully mixed in the developer nor electrically charged to a necessary value. In said developing apparatus, toner concentration in all of the transport passages is difficult to be desirably and uniformly maintained because toner concentration in each of the first to third passages would vary, thereby resulting in such drawbacks that fog appears on an image or powdery mist of the developer leaking out of the developing apparatus stains peripheral apparatuses.